1. Field of the Invention
The present invention relates to a camera to be powered, when attached to a motor drive device, by the power source for said motor drive device.
2. Description of the Prior Art
There is already known a camera in which a constant voltage circuit is powered, when it is attached to a motor drive device and in response to the actuation of the shutter button, by a power source for driving a motor in said motor drive device, thereby energizing a shutter control solenoid and other components by the output voltage of said circuit. Such camera is advantageous in preventing power loss in the constant voltage circuit since it is powered only when the shutter button is pressed to activate the shutter control solenoid etc. Also there is known the use of an oscillating circuit containing a piezoelectric vibrating element made of quartz or a ceramic material for effecting the control of the shutter solenoid or the sequence control of electromagnetic shutter releasing device by means of the stable specific frequency of such vibrating element. However such oscillating circuit involving the piezoelectric element often has to be continuously powered in a camera requiring critical timing for picture-taking, as such circuit requires a relatively long time to reach a stable oscillation after the start of power supply.
Thus, if the shutter control solenoid and the oscillating circuit are powered by the power source for the motor drive device through a constant voltage circuit to be switched on in response to the actuation of the shutter button, there may result a perturbed shutter control due to the picture-taking operation initiated before the oscillating circuit reaches a stable oscillation, or there may be lost an important picture-taking opportunity because of an excessively long time period before the shutter can be released. On the other hand if the constant voltage circuit is continuously powered to activate the oscillating circuit regardless of the manipulation of the shutter button, there will result a considerable power loss in said constant voltage circuit as it has to be designed to provide a large power for driving the shutter control solenoid etc. In order to avoid these drawbacks the motor drive device can be provided, in addition to the aforementioned constant voltage circuit, with a separate power supply circuit of low power consumption exclusively for continuously driving the oscillating circuit, but such arrangement requires an increased number of terminals for said constant voltage circuit and said separate power supply circuit respectively on the motor drive device and the camera itself, leading to a lowered reliability.